Method of producing c1-c3 dialkyl hydrogen phosphites



Jan. 15, 1952 D. H. CHADWICK y METHOD OF PRODUCING C, -Cg DIALKYLHYDROGEN PHOSPHITES MEDOC 2 SHEETS-SHEET l FiAled Sept. '7,

BYgmu/@M ATTORN EY Jan- 15, 1952 D. H. cHADwlcK METHOD ov PRODUCINGCl-c5 DIALKYL HYDROGEN PHOSPHITES 2 SHEETS- SHEET 2 Filed Sept. 7, 1949FIGURE 3 K R. WO Dm mw .Y CmQE H. DN m m V. T m YA B )L|).D\IF|)7 9 9 Ow o .0|

E L R. L. w m w H be carried out in rela Patented Jan. 15, 1952 aunirti-jol STATES infra-1vry orifice rtoocihe.olloginrlitkr HYDROGENPHOSPHITES Dacia n.; Chadwick.- Anniston, ma, assignor toMonsantohemical Company, St. Louis; Mo., a corporation'of Delaware Ipi-letonsfr 7, 1e4ei'ser`Nd1143'za isl (or 2604-461)- The presentinventionrelate's to -dialklylA hydrogen phosphites containing from onetothree' car- 'con atoms and to a novel method of" producing same.

` An object of the irive'rition.is to* provide an economically andcommercially feasible' method of producing thev above compounds" yAnother object is to providea method of pro# ducing Cl-Cg dialkylhydrogen phosphites` from phosphorus trichloride and the" correspondingaliphatic alcohols in whichthe reaction is carried out substantiallyinstantaneously.

A further object is to' provide' a continuous method of preparing Cr-C*dialkyl: lhydrogen phosphites from the abovereactantsg; wherein the`reaction temperature is controlled` by internal cooling. v

A still further object is tof' provide al method which results in theproductionpf theCirxtoiCa dialkyl hydrogen phospl'iitesin substantiallyimproved yields over conventional'methdds. Other objects and advantages'ofythe` present invention will become apparentjtoj those skilled in theart as the description-proceeds. The instant inventionconstitutesadecided 'mrproveinent upon, conventional methods o cucine the C1 to C3@alkyl-hydrogen phqsphliez' from phosphorus trichloride andth ecorresponding alcohols- Moreovelf. thghreht rheihol: Geh

In prior methods, it has benpiopos duce the C1-C3 dialkyl" hydrog'e'plireacting the corresponding'ialcoho phorus trichloridein a" pot-type re rtemperature controlis effected'b ndirec cooljing vand by means ofdilutingvvv solv`e nt s 'such benzene. However, when Vthe 1 e broughttogether en massein'jthis diflicult to achieve satisfactoryj'miinn `contacting of thev reactantsfandfunifornrfte pifa 'ture control Withtheresultthat1 sp tsr end to develop causingfl'ocaliz'ed'decipositiowith correspondingly lower product yields'. Thusby the above methods;veven with meticulous care andcontrolyit has not: been possible `toconsistL entlybtain ajpifduct' yield inV excess of 80% of theory; basisPG13. Moreove'n they'have the dis'` advantageof involving batchoperations and'cf requiring unduly large andi expensive' equipment forlarge volume production and also agitators fornrixin'g thefreactants',which lead to excessive power requirements and mechanical troubles dueto lakagefthrough th'stufng box for' the:` a'gil tator shaft.'

In accordance with the' present invention',v the reaction of' the C1`C3-aliphatic' alcohols' with phosphorus trichloride is accomplishedsubstantiall'y instantaneously by mixing the reactants andan inertorganic refrigerant in a shortv tubular nozzle' and sprayingv or'atomizing the resultingproduct into a collecting chamber' whichispreferably maintained at substantially atmosphericpre'ssure. Asajr'esult of the exothermic heat" generated by the alcohol-phosphorustrichloride reaction, evaporation of an equivalent amount of refrigerantoccurs; thus accounting for the observed large pressure drop in thenozzle. The mixture' comprising dialkyl hydrogen phosphil'fe", hydrogenchloride and vaporized refrigerant leavingithe nozzle at high velocitysprays into the collection chamber, which is designed to sepa-1 rat theiinelyv divided ester from thel vaporized refrigerant and undissolvedhydrogen chloride gas: Any liquid refrigerant leaving the nozzle Willevaporate in the collection chamber and will lower the temperaturethereof but,will not niaterially affect the nozzle temperature. VTheproducts hnamely, the Ci-Cs dialkyl hydrogen phosp hites. hydrogenchloride and the refrigerant, mayl thereafter' be separated in anysuitable niannerl E br more complete understanding of the in si'.a'rii'."invention;'referenceis madetoA thegaccoinpanyingfdrawings, itbeing understood'that' modi'- parent to those skilled in the art may bemade as desired without departing from the scope of the invention.

Figure l is a side elevational View, partly in section, of laboratoryapparatus successfully used in practicing the present invention.

Figure 2 is an enlarged vertical sectional view of the spray orcollecting chamber and nozzle used in Figure l, showing their structurein greater detail.

Figure 3 is a vertical sectional view of another embodiment of theinvention, showing the spray nozzle, spray chamber, float valve, andauxiliary parts. In this view, the float valve is in the closedposition.

Figure 4 is a side elevational view of the valve stem and the perforateddisc with which it cooperates to control the discharge of the reactionproduct from the spray chamber. In this View, the float valve is in theopen position.

Referring to Figures 1 and 2, reference characters I and 2 indicateflasks for containing 'ai Ci-Ca aliphatic alcohol, for example, methylalcohol and phosphorus trichloride respectively andl referencecharacters 3 and 4 are scales used for periodically weighing the abovereactants.

Reference character 5 is a cylinder of a suitable refrigerant such asmethyl chloride.

The alcohol iiows from iiask I via stopcock 6 into line 'I which leadsto thev intake Bof a pump J 9. The alcohol is then pumped by way of lineI0 through rotameter Iljand from there by way of line I2 into spraynozzle I3. y

The phosphorus trichloride is conveyed through stopcock I4 into line I5which is connected to the intake I6 of pump Il. From pump I'I, thephosphorus trichloride is passed via line I8, rotameter I9 and line 20into nozzle I3.

The refrigerant is conducted through valve 2 I, line 22, rotameter 23,line 24, coils 25,"line '26, valve 21 and line 28 into nozzle I3. Thecoils 25 are immersed in a cooling medium 25A contained in tank 25Bwherein the refrigerant is precooled to the desired temperature. Theintimate mixture of alcohol, phosphorus trichl-oride and refrigerant issprayed through the nozzle outlet 29 into chamber 30 which is providedwith packing 3 I vto prevent entrainment of product by escaping vaporsand gases, a 'vent 32 for discharging said vapors and gases from Athesystem and a discharge line 33.

The spray chamber 3U is also equipped with a thermometer line 31 into astripping column 38. This column is equipped with thermometers 39 andvlill at the points indicated, vacuum connection 4I for maintaining thedesired reduced pressure therein, Berl saddles or other suitable packing42, an electrical heating coil 43 and a discharge line 44,.

The electrical heating coil heats the dialkyl hydrogen phosphite at thebottom of the stripeping column 38 so that the temperature progressivelydecreases from the ybottom to the top thereof. chloride concentrationprogressively decreases from the top toward the bottom of the column andit is essential that the heat applied at'vthe various points thereindecrease as the hydrogen chloride c-oncentration increases, otherwisesubstantial decomposition of thedialkyl hydrogen phosphite lwill occur.The heating of thestrip ping column at the bottom to a reboiler tem'-This is important since the hydrogen -V perature corresponding to theboiling point of the product at the operating pressure results inessentially complete separation of hydrogen chloride and small amountsof refrigerant and unreacted materials from the dialkyl hydrogenphosphite.

The crude dialkyl hydrogen phosphite being substantially free of theforegoing impurities iiows continuously at a controlled rate throughlines `44 and 41 into the product still column 48 which is provided witha thermometer 46 and is attached by connection 5U to still pot 5I, thelatter being provided with a thermometer 52, and a suitable heatingmeans 53. The still column 48 is provided with Berl saddles or othersuitable packing 54 and a take olf tube 55 leading to a condenser 56.

The condenser 56 has a vacuum connection 5] provided with a takeoff line58 leading by way of stopcock 59 and lines 66 and '5I into productreceiver 62. Stopc-ock 59 is provided with an outlet 59A so that theproduct receiver .62 may be connected to the atmosphere through lines 60and 6I.

The condenser is also connected by stopcock controlled line 63 with theproduct receiver 62 and by a similarly controlled line 64 with the topof the still column 48.

By regulating-stopcocks 65 and 66 in lines 63 and S4 respectively, theamount of condensed product flowing to the product receiver or to thetop of the column may be controlled, thus providing means for regulatingtlie reflux ratio.

The stillY pot 5I is provided with a high boiling solvent such asphenylcyclohexane which facilitates distillation of the dialkyl hydrogenphosphite Without substantial decomposition of the latter. This product,as hereinbefore indicated, is condensed in condenser 56 and recovered inproduct receiver '62; the high boiling solvent remains inthe still pot5I to be used over and over again.

The invention isillustrated but not limited by .the following example.All parts are by weight.

Methyl alcohol, phosphorus trichloride and precooled methyl chloridewere fed continuously to nozzle I3v and sprayed into chamber 3U at ratescorresp-onding to 7.91, 5.57 and 18.5 parts per minute, respectively.This was done for 3 hourszand 31 minutes during which time the vaporizedmethyl chloride maintained the reaction at a temperature of 20 C.

The resulting dimethyl hydrogen phosphite was continuously conductedinto stripper 38 where hydrogen chloride, methyl chloride and unreactedmaterials were continuously removed by heating the crude product to areboiler temperature-of 99 C. while under an absolute pressure of ilvmm.v of mercury.

The -dimethyl hydrogen phosphite product being freed of the foregoingimpurities was continuously charged into still pot 5I containing 200parts of phenyl cyclohexane, from which Asubstantially pure dimethylhydrogen phosphite was continuously recovered by distillation at atemperature of 56?" C. and an absolute pressure of about l1 mm.ofmercury. A total of 1228 parts'of dimethyl Ahydrogen phosphite wasobtained which corresponds to a yield of 959i,- of theory, basis PG13.The several runs given in the following table further illustrateconditions of operation under which satisfactory results from thestandpoint .f www yield. are .Qbian'ed These funs ver@ carried out inthe above apparatus, the conditions differing in the manner indicatedthose given in the foregoing specific example.

cot recovers ao' ouriscationfsystejm (not shown) which includes stripperfor @omitting residual Table Totti i'ecfflts Y t L fvg' Elovv'hlats Bi'Avg. Prossres, min.V Hg Runy Total-frime; rarzs'y wt. Molar. No. Min.AExcess .i

tot einen. chi-d1 i onion rou oHioH ous-o1 Reactor' stripper l suuisjo'175, o 84o al4a ooo 7' I s 185 s 11,316 .1. 5.03 15o 21 1 10 251 2,029 I-2 5. 5,3 21.2 15o 47, A 14 297 2,033 2 4:98' 17.0 750 ICIU i l? t 1.munie L iwf.. 1w .f. d ah...

Avg.l Temperatures, a C. I l

v b 'Product Parts e Run No. Stripper Still NYTQIMHPIE DlzteluEtI-'Pir-Reactor K Y Y l listi ed) l Top. y Middle Bottom Bottoni Feed d -41 to z2r A 47. 45j I iat; f so 17 29: '70'A i 54 9,525 SS --4U 68'5 i .985 601,515 9i -20 A -25 47 L 115 64 R485 89 14DMHP dimethyl hydrogenphosphite.

l Referring to Figures 3 and 421 reference character 'iii representsaspray or collection chamber composed of glass"V units H; 'i2v and 'Htsecured together by clamping' devices' 'i4' and i5.

The top of unit H is" covered by closuredisc 16 which is secured invposition byr4 a suitable ,i

clamping device'A TT. This' disc carries af nozzle 'i3 having an oriice'ifBlwliichcommunicates with feed linesv 80 and 8|: Thenozzleissiipplied with phosphorus trichlorideY by wat: of line 810'" and withan alcohol-#refrigerant mixture-1h31 lineal, the latter being connectedby linee! tothe a1*- cohol and refrigerant feed lines 83' and Bitfespectively. -A pressure gage 85' located at' the juncture of lines 81and 32`A to indicate' thepres'isure drop across nozzle`18'. V

Unit 'l2 is' in the form of a' cross and its com'- ponent partsarecircularin' cross section. yThis uniti is provided with'a closuredisc` 86 whichf is secured in place byV clamping"- ineens 81. This disccarries a thermocouplefor another 'empraf ture sensitive device 88which' actuates" an infstrument which in turn` automatically controlsthe temperature of'tlriereactionby regulating the owof refrigerant to'the nozzle. l

The bottom of unit 13 is closed by: means of disc 89 having an opening"9U which serves" 'as a guide forV valve stem 9il and all`s`o` asiaoutlet forV the' product. Tle valve stein" 9l" xtedsf'p ito unit 72 and'Carries a' spl'iicl'/ glss'jt 92' at a point near" its upper en the oatbe secured in position by' nuts' 93 and 941 The lower portion ofthevalve' sternfedeiols through unit which is connected t'o T3 by clamping,means S5, and also into unit 9'!y which is leizltov unit 95 by a similarclamping means 98". At' ai point near Ythe bottom f disc'4 879,1v thevalve stein 91 provides with a detent se' which iirn'itsits upwardmovement as it is' raised by' oat 92 due tdtl'e buoying action of theaccumulated'productl At the jrncture of units 95an'd`91, a` separatingdisc Iil is located containin'ganopening" IUI which serves as a valveseatfr theita'pered riortion |62 of valve stem 9|, asa gide for theelongated portion I 03-oftherva1vejstrn'andalso as a productdischarge-opening leadin'g tif-'proditrg/drogen chlorideand low boilingimpurities-,- and a. tractionating column and stillpot for separatinghigh boiling impurities?.-y

VUnit 'F2 is also connected by clamping means Nie to unit ist' which isin the4 form of an elbow of circular cross sectionJ and the latter inturn attachedto unit m6, also of circularA cross section,i by' clampingmeans lill. UnitsiEv and il' arek separated by perforated plate Hi8which serves as a support for Raschig rings or another .suitable packingille. The' perforated plate' per 4mits hydrogen chloride, refrigerantand entrained product to pass through vandv the packing minirnizesrlossl of theY desired product While allowing hydroge'n chloride andrefrigerant to escape from thesystem'.

In practicingthe method of the instant inventionk in the aboveapparatus; the phosphorus trichloride', aliphatic alcohol' andrefrigerant are continuously suppliedV to nozzle i8 Where they areintimately mixedr and sprayed into chamber The' reactants -a're fedtothe nozzle at ratespro- -viding substantially 3 moles of the' alcoholto l of phosphorus trichloride, while the refrigerant ischarged at aratefnaintaining a temperature in the range ofy vil C. and 5 C.` andpreferably the range of -2G C. to #19 C. II the temperature rises" aboveapredetermined value, the therm'ocoupie e8 whichis parto* aC system (notshown) regulating the-refrigerant feed; eiects an increaseinther'low'rate of the refrigerant and thu'sf lowers the reactiontemperature to thefde- -sired level; ifit'he' ternperatl'ire`V fallsbelow the above-value, then thefthermocouplefreduces the flow rate ofthe refrigerant and raises the reacu tion' temperature' tol the desiredvalue.

The crudereactionrpioduotmet accumulates The crude product. dischargedfrom the spray chamber is conducted continuously to a purification andrecovery system (not shown) similar to the one described in connectionwith Figures 1 and 2. This system includes a stripper for continuouslyremoving residual hydrogen chloride and low boiling impurities and afractionati-ng column and still pot for .separating relatively highboiling impurities.

The vaporized refrigerant, hydrogen chloride and entrained dialkylhydrogen phosphite pass through unit and perforated disc |08 intopacking |09, where the ester is separated and the vaporized refrigerantand hydrogen chloride are allowed to escape from the system, the esterbeing returned to the spray chamber. The hydrogen chlorideis recoveredin any well known manner and the refrigerant is recovered, recompressed,precooled and repeatedly returned to the process.

The following is an illustrative example of the method of practicing thepresent invention in the foregoing apparatus.

Methyl alcohol, phosphorus trichloride and precooled methyl chloridewere fed continuously to nozzle 't8 and sprayed into spray chamber l ataverage rates corresponding to 8.43, 11.71 and 31.6 lbs. per hourrespectively. This operation was carried out for a period of 'I hoursduring which time the vaporized methyl chloride maintained the reactiontemperature Within the range of -11 C. to -8 C.

The resulting dimethyl hydrogen phosphite was -continuously conducted toa stripper (not shown) wherein hydrogen chloride, methyl chloride andunreacted materials were continuously removed by heating the crudeproduct to a reboiler temperature of about 103 C. while under anabsolute pressure of about 133 mm. of mercury.

The dimethyl hydrogen phosphite product, after being freed of theforegoing impurities, was continuously charged to a combinedfractionating column and still pot containing phenylcyclohexane, fromwhich substantially pure dimethyl hydrogen phosphite was continuouslyrecovered by distillation at a temperature of about 58 C. and anabsolute pressure of about 22 mm. of mercury. A total of 61.0 lbs. ofdimethyl hydrogen phosphite was obtained which corresponds to a yield of93% of theory.

In carrying out the method of the instant invention, phosphorustrichloride and the Ci-C'a aliphatic alcohols are reacted together in amolar ratio of substantially 3 moles of alcohol to 1 mole of thetrichloride, but higher ratios may be used if desired. However, it isnot desirable to use more than and preferably not more than 2% molarexcess of the alcohol.

As to the temperature of the reaction, this may fluctuate widely so longas temperatures at which substantial decomposition of the desireddialkyl hydrogen phosphite are avoided. In general, the reactiontemperature is maintained within the range of about -41 C. up to about 5C. and within this range'a temperature of about 10 C. to -20 C. ispreferred.

The reaction temperature is controlled by spraying the reactants inintimate contact with an inert organic refrigerant which vaporizes andabsorbs the heat of reaction. Any organic compound which is inert underthe reactive conditions of the process and does not boil above 0 C. atatmospheric pressure may be used. Typical examples of .these aremethane; cyclopropane; isobutane; propane; methyl ether;

carbon tetrafluoride; 1-chloro-1,1,2,2pentauoro ethane;1,1-dichloro-l,2,2,2 tetranuoroethane; 1,1-difiuoroethane;hexauoroethane;

1,1,1-trifluoroethane; ethyl fluoride; fluoroform;

isopropyl fluoride; chlorodifluoro methane; chlorotrifluoro methane;methyl chloride; difluoromethane; methyl fluoride; 2,2 difluoropropane;propyl iiuoride; dichloro difluoro methane; monochloro-tetraiiuoroethane; octafluoropropane; decafiuorobutane; tetrafluoromethane andhexauoroethane.

Of the foregoing refrigerants, methyl chloride is preferred since it iscommercially available in the desired quantities. Moreover, its use inthe production of vvdimethyl hydrogen phosphite is particularlyadvantageous since it is a product of the reaction and therefore doesnot further contaminate the product. Furthermore, it may be readilyseparated from the dimethyl derivative and repeatedly used and anylosses of refrigerant which occur during such reuse are continuouslyreplenished by further reaction between methyl alcohol and phosphorustrichloride.

The amount of refrigerant which should be used varies not only with thereaction temperature to be maintained but also with the refrigerantselected. The lower the temperature that is selected the greater is thequantity of a given refrigerant that must be used and vice versa.Moreover, the quantity of refrigerant required to maintain a givenreactiontemperature depends upon its latent heat of vaporization, thevalue of which is available in the literature or readily determined byone skilled in the art.

In the production of dimethyl hydrogen phosphite in which methylchloride is the refrigerant, the latter is generally employed in aweight ratio of about 2-5 of methyl chloride to 1 of methyl alcohol.However, higher or lower ratios of methyl chloride to methyl alcohol mayoe employed depending upon the reaction temperature to be maintained.

As to the other refrigerants, no attempt will be made to define morespecically the quantity which should be used since this is dependentupon the above-mentioned factors and can be readily determined by thoseskilled in the art.

The reaction between the Ci-Cs aliphatic alcohols and phosphorustrichloride takes place substantiallyinstantaneously and is completed sofar as it is possible to ascertain in the space of time required forpassage of material through the spray nozzle.` In passing through thenozzle, reaction between the above reactants occurs liberating heatwhich causes rapid vaporizaton of the refrigerant within the nozzle. Thelarge volume of vapor thus liberated within the nozzle causes a pressuredrop across the nozzle which is substantially higher than that observedfor the same mass ow of liquid. The magnitude of the pressure dropdepends upon the rate of evaporation of the refrigerant which in turndepends upon the vapor pressure of the refrigerant, the heat of reactionand to a lesser degree upon the degree of dilution of the reactants.When operating on a large scale using drilled metallic nozzles, thepressure drop is at least 25 lbs. per square inch vand usually less thanlbs. per square inch. However, in practice of the instant invention, it`is preferred to select a nozzle and so correlate the other conditionsasto obtain a pressure drop across the nozzle of about 30-35 lbs. persquare inch.

As hereinbefore indicated, the mixture of re- .frigerantand dialkylhydrogen phosphite leaving the nozzle is introduced into a collectingchamber which is operated at substantially atmospheric pressure. Byreason of the nestate of 'subdivision of the above product,l any' liquidor gaseous refrigerant contained therein is rapidly and subl stantiallycompletely separated by vaporization. After separation from the dialkylhydrogen phosphite, the refrigerant is recovered,` compressed andliquefied for reuse in the process.

The crude dialkyl hydrogen phosphite product is conducted to a strippingtower where it is gradually heated, preferably under reducedpressure, toremove hydrogen chloride and low boilingimpur-ities. The strippingtemperature varies with the'p'ressure selected, the lower the pressuretheilower the temperature which may be used and-vce versa. At a selectedoperating pressure, the'.reboiler temperature, that is the temperatureatthe bottom of the stripper, is maintained at the boiling point of thedialkyl hydrogen phosphite being treated.

In the removal of hydrogen chloridel and lou. boiling impurities fromdimethyl hydrogenphosphite, a stripping pressure of from about lo to 150mm. and preferably from. about 40'to 100 mui.

of mercury is employed. The stripper reboilei' temperature isconveniently maintained at the boiling point of dimethyl hydrogenphosphite at the operating pressure selected.. In practicejthis involvesa reboiler temperature Within the range If desired, stripping pressuresand temperatures outside the above limits may be used providedsubstantial decomposition of the desired dialkyl hydrogen Vphosphite isavoided.

The stripping operation may be carried out in a number of other ways.For example, theihydrogen chloride may be removed by adding benn zene,carbon tetrachloride or another suitable solvent and then sweeping outthe above acidby neutralizing the product with ammonia or ari-- othercompound which forms an insoluble chloride and separating the latter byfiltering or centrifuging.

After removal of hydrogen chloride and low boiling impurities, theCLCdialkyl hydrogen,

phosphite product is further purified by removal of high boilingimpurities. This may be accomplished by dissolving the above product ina suitable inert organic solvent and fractionally distilling the esterfrom the solvent which'r'etains the impurities; or by heating the crudeproduct in contact with an inert organic material 4which serves not as asolvent for the impurities'- but merely as a heat exchange medium forAeffecting the distillation. In carrying out the above puri- I ficationoperation, any inert relatively high boiling organic heat exchangingmedium or solvent which does not form an azeotropic mixture with thedialkyl hydrogen phosphite and which `boils at a temperaturesufiiciently above the boiling point of the product to permit efcientfractiona tion may be employed. In practice, it is preferred to usephenylcyclohexane, but any equivalent or. ganic heat exchanging mediumwhich iS Preft" i0 ably immiscible with vhigh boilers and boih withinthe range of 90 C. to 130 C. at mm,

-mercury may be employed. By high boilers" `I mean the high boilingimpurities left as a residue after the dialkyl hydrogen phosphites havebeen removed from the crude reaction product.

'I'he distillation is effected at a temperature at least equivalent tothe boilingv point of the dialkyl hydrogen phosphite being separated,but below that temperature at which substantial decomposition of thisproduct takes place. The distillation pressure may fluctuateconsiderably, but in practice pressures in the range of about 10 mm. toabout mm. of mercury are preferred. The optimum distillation temperatureand pressure will, of course, vary with the dialkyl hydrogen phosphitebeing distilled, but for the dimethyl derivative the most satisfactoryresults appear to be obtained at a temperature of about C. and apressure of about 25 mm. of mercury.

By the expression C1-C3 diallryl hydrogen phosphites, I mean dimethylhydrogen phosphite, diethyl hydrogen phosphite and diisopropyl hydrogenphosphite. Normal dipropyl hydrogen phosphite is not intended since theadvantages of the present invention do not apply thereto or to dialkylhydrogen phosphites having a greater number of carbon atoms.

The foregoing description has been limited to thereaction of the C11-C3aliphatic alcoholawith phosphorus trichloride, but it is to be clearlyunderstood that phosphorus tribromide may be used in place of thetrichloride. v

`Although the present invention has been de scribed with reference to aparticular embodi- 'menu it will be apparent to those skilled in the artthat variations and modifications of this invention can be made and thatequivalents can be substituted therefor without departing from theprinciples and true spirit of the invention.

What I claim is:

l. The method of making dialkyl hydrogen phosphites, which comprisesspraying into a collection zone, a mixture containing an aliphaticalcohol selected from the group consisting of methyl, ethyl andisopropyl alcohols, a phosphorus halide selected from the groupconsisting of 'phosphorus trichloride and phosphorus tribromide and avolatile inert organic refrigerant which does not boil above 0 C. atatmospheric pressure, said refrigerant being employed in an amountsufiicient to maintain the reaction ternvperature within the range ofabout -4l9 C. to

about 5 C.

2 "I'he method of making dialkyl hydrogen phosphites, which comprisesspraying into a col- "lection zone, a mixture containingV an aliphaticalcohol selected from the group consisting of methyl, ethyl andisopropyl alcohols, phosphorus `triclfilo'ride and a volatile inertorganic refrigera'nt which does not boil above 0 C. at atmosphericpressure, said refrigerant being employed in an amount sufficient tomaintain the reaction temperature within the range of about 41 C. toabout 5"l C;

3. The method of making dialkyl hydrogen phosphites, which comprisesspraying into a collection chamber, an aliphatic alcohol selected fromthe group consisting of methyl, ethyl and isopropyl alcohols, phosphorustrichloride and a volatile inert organic refrigerant which does not boilabove 0 C. at atmospheric pressure, refrigerant being employed in anamount suffcient to maintain the reaction temperature within the rangeof about 4lQ C. to about 5 C'. and

' 1 l said reactants being employed in the molar ratio of substantially3 moles of the alcohol to 1 mole of phosphorus trichloride.

4. The method of making dialkyl hydrogen phosphites, which comprisesspraying into a collection zone, an aliphatic alcohol selected from thegroup consisting of methyl, ethyl and isopropyl alcohols, phosphorustrichloride and a volatile inert organic refrigerant which does not boilabove C. at atmospheric pressure, said reactants being employed in amolar ratio of substantially 3 moles of alcohol to 1 mole of phosphorustrichloride and said refrigerant being employed in an amount maintaininga reaction temperay ture within the range of about 20 C. up to about 10C.

5. The method of making dialkyl hydrogen phosphites, which comprisesspraying into a collection zone at substantially atmospheric pressure,an aliphatic alcohol selected from the group consisting of methyl, ethyland isopropyl alcohols, phosphorus trichloride and a volatile inertorganic refrigerant which does not boil above 0 C. at atmosphericpressure and recovering the dialkyl hydrogen phosphite produced, saidreactants being employed in a molar ratio of substantially 3 moles ofalcohol to 1 mole of phosphorus trichloride and said refrigerant beingused in an amount maintaining a reaction temperature of about 20 C. toabout 10 C.

`t. The method defined in claim 5, wherein the resulting product issubjected to a stripping operation to remove hydrogen chloride and lowboiling impurities.

'7. The method defined in claim 6, wherein the crude product issubjected to vacuum distillation While in contact with an inertrelatively high boiling solvent, said distillation being carried out ata temperature at least equivalent to the boiling point of but below thatpoint at which substantial decomposition of the dialkyl hydrogenphosphite takes place.

8. The method of making dimethyl hydrogen phosphite, which comprisesmixing together methyl alcohol,. phosphorus trichloride and methylchloride and spraying the resulting product into a collection zone, saidalcohol and said trichloride being employed in the molar ratio ofsubstantially 3 moles of the alcohol to 1 mole of phosphorus trichlorideand said methyl chloride being used in an amount maintaining thereaction temperature within the range of about 41 C. up to about 5 C.

9. The method defined in claim 8 wherein methyl chloride is used in anamount sufficient maintain the reaction temperature at about 20 C. toabout 10 C.

10. The method defined in claim v8 wherein methyl chloride is used in aweight ratio to methyl alcohol of from about 2 to about 5 of the formerto about l of the latter.

l1. 'Ihe method of making dimethyl hydrogen phosphite, which comprisesmixing together and spraying methyl alcohol, phosphorus trichloride andmethyl chloride into a collection zone and 12 heating the collectedproduct at a temperature suiiicient` to remove hydrogen chloride and loWboiling impurities, said methyl alcohol and said phosphorus trichloridebeing employed in the molar ratio of substantially 3 moles of alcohol to1 mole of the trichloride and said methyl chloride being used in anamount suirlcient to maintain the reaction temperature Within the rangeoi about 41 C. to about 5 C.

12. The method of making dimethyl hydrogen phosphite, which comprisesspraying together methyl alcohol, phosphorus trichloride and methylchloride into a collection zone maintained at substantially atmosphericpressure, gradually heating the collected product to a temperaturesuicient to remove hydrogen chloride and low boiling impurities, andthen vacuum distilling a solutionof the dimethyl hydrogen phosphite in arelatively high boiling inert organic solvent at a temperature at leastequivalent to the boiling point of but below that point at whichsubstantial decomposition of said dimethyl hydrogen phosphite takesplace, said methyl alcohol and said phosphorus trichloride beingemployed `in a molar ratio of substantially 3 moles of alcohol to 1 moleof phosphorus trichloride and said methyl chloride being employed in anamount suilicient to maintain the reaction temperature within the rangeof about 20 C. to about 10 C.

13. The method of continuously producing dialkyl hydrogen phosphites,which comprises continuously spraying into a collection zone analiphatic alcohol selected from the group consisting of methyl, ethyland isopropyl alcohols, phosphorus trichloride and a volatile inertorganic refrigerant which does not boil above 0 C. at atmosphericpressure, heating the collected product to a temperature suiiicient toremove hydrogen chloride and lovsT boiling impurities and continuouslydistilling a solution of the resulting crude product in a relativelyhigh boiling inert solvent at a temperature above the boiling point butbelow that point at which substantial decomposition of the dialkylhydrogen phosphite occurs, said aliphatic alcohol and phosphorustrichloride being employed in a molar ratio of substantially 3 moles ofthe alcohol to 1 mole of the phosphorus trichloride and said refrigerantbeing employed in an amount maintaining the reaction temperature withinthe range of about 41 C. up to about 5 C.

DAVID H. CHADVVICK.

REFERENCES CITED The following references are of record in the file ofthis patent;

UNITED STATES PATENTS Number Name Date v 2,175,509 Rogers et al Oct. 10,1930 2,187,244 Mills Jan. 16, 1940 2,214,254 Mills et al Sept. 10, 3.940I2,426,691 Jenkins Sept. 2., 194'!

